1. Field of the Invention
The present invention relates to a method and apparatus for severing work objects and, more particularly, to such a method and apparatus which have particular utility in severing laminate materials cleanly and precisely without damage to the severed edges thereof while possessing the capability of producing intricate configurations and which can achieve such operational objectives on an assembly line basis.
2. Description of the Prior Art
The manufacture of products, particularly where manufactured on an assembly line basis, presents unique difficulties which may not be encountered in the construction of a single, or a small number of such products. While most products could be hand fabricated with the precision and operational objectives which may be desired, the necessity for the mass production of such products frequently requires that these operational objectives be compromised. While some of these compromises may be tolerable, others may simply render the product, as originally conceived, impractical. However, even in the case of the compromises which can be tolerated, the desirability of avoiding such compromises may be substantial.
In the manufacture of containers, for example, it has been known to employ laminated cardboard, paperboard, or boxboard, to achieve a number of attractive operational benefits. One beneficial form of construction calls for a pair of end walls of rather substantial thickness to be employed, about which is extended a wrapper so as to form a container having flaps which can be folded into sealing relation to the interior of the container. The wrapper is of relatively thin construction which permits it conveniently and precisely to be cut from a panel of such material. The end walls, however, are of such a thickness that such severing is difficult without some degree of damage thereto.
One material from which such end walls have been fabricated is triple wall corrugated boxboard laminate material. This is a laminated cardboard, or boxboard, material having three layers of corrugated cardboard with each layer consisting of one corrugated sheet overlaid on opposite sides by flat sheets. This form of construction for the end walls is particularly desirable because it is very strong, holding its shape during assembly of the container and in use while being of very light weight and inexpensive construction. However, conventional methods for manufacturing such end walls require sawing through the laminated triple wall material using circular saws or the like. The action of such saws typically crushes the flutes of the corrugated laminations along the courses of such severing weakening the integrity of the end walls. Furthermore, conventional methods are incapable of staying within the optimum design tolerances thereby interfering with the assembly and use of the containers so formed.
These problems in the formation of end walls from such triple wall laminate material are compounded when the containers are to be of the interlocking type having projections along the upper edges of the end walls and recesses in the lower edges of the end walls. Such containers are operable to interfit with each other wherein the projections of a lower container mate with the recesses of a container immediately thereabove to form a stack of substantially increased unitary integrity. Conventional construction methods call for such projections and recesses to be formed in the end walls using saws, or other types of cutting blades. The saws are required to follow paths relative to the end walls which are intricate and create even greater stress on the corrugated layers of the triple wall material than in the case of end walls without projections or recesses. This stress results in rather significant damage to the marginal edges of the end walls so formed. The flutes of the corrugations are frequently crushed. Portions of the laminate layers fray or tear away entirely. Even more damaging, the optimum design tolerances for the projections and recesses are extended to the point of significantly diminished utility.
As a direct consequence, the containers so formed frequently do not have projections and recesses which can adequately interfit when the containers are disposed in stacked relation thereby presenting a myriad of problems in the formation, packing, transport, storage and unpacking of such containers. The projections may be so weakened as to collapse under the weight, or lateral adjustment, of a container rested thereon during stacking. Furthermore, the weakening of the marginal edges of the end walls in such conventional forming operations significantly weakens the overall structural integrity of such containers otherwise producing less than desirable consequences.
Therefore, it has long been known that it would be desirable to have a method and apparatus for severing work objects which are operable to form such work objects within tolerances not heretofore achieved in the art and are capable of unvarying precision throughout a long operational life; which have particular utility in the severing of laminate work objects such as end walls employed in the construction of containers; which are operable to form work objects from such laminate materials having intricately formed marginal edges; and which are fully capable of the mass production of such work objects with unvarying accuracy without the host of difficulties presented by prior art methods and apparatuses.